1. Field of the Invention
This invention relates to a push type thermal device and method of making the same as well as to a resilient stem seat for such a device and method of making the same.
2. Prior Art Statement
It is known to provide a push type thermal device having a resilient stem seat provided with an opening in one end thereof and receiving an actuating stem in the opening that is adapted to reciprocate in a longitudinal direction in the opening in response to the thermal expansion and contraction of a charge of material in the device and only operatively acting on the other end of the stem seat in the aforementioned longitudinal direction.
For example, see the following U.S. patent:
(1) U.S. Pat. No. 3,046,787--Wagner
It appears that the resilient stem seat of item (1) above has the diameter of the opening therein substantially the same as the diameter of the actuating stem being received therein except that a narrow section of the stem seat adjacent the open end of the opening has a reduced diameter through which the stem is press fitted to not only form a seal between the stem and the stem seat, but also between the stem seat and the casing carrying the same.
Another type of thermal device comprises a squeeze-push type wherein the resilient stem seat has a considerable length thereof radially surrounded by the charge of material which, when expanded, will squeeze the stem seat radially inwardly to squeeze and, thus, push the actuating stem in a longitudinal direction relative to the stem seat whereby the radial collapsing action of the stem seat for a squeeze-push type thermal device is completely different than just the longitudinal collapsing action of the stem seat for soley a push type thermal device.
For example, see the following U.S. Patent:
(2) U.S. Pat. No. 3,016,747--Vernet
It appears that the opening in the resilient stem seat has a diameter less than the outside diameter of the actuating stem so that the actuating stem must be press fitted in the opening of the stem seat substantially throughout the entire length thereof during the assembly of the stem within the stem seat.
Various means have been provided to tend to reduce rupture of the resilient stem seat of the squeeze-push type thermal device.
For showings of such improvements in the squeeze-push type of thermal elements, see the U.S. Patent to Vernet, No. 3,064,477; U.S. Patent to Baker, No. 3,080,756; U.S. Patent to Daly et al, No. 3,149,455; U.S. Patent to Winter, No. 3,420,105; and U.S. Patent to Dyhr-Mikkelsen, No. 3,832,850.